Unsaturated polyesters are useful in the fabrication of a wide variety of products. They are made by reacting dibasic acids, such as phthalic anhydride, maleic anhydride, etc., with difunctional alcohols, such as ethylene glycol, propylene glycol, etc. By varying the starting monomers, some can be made spinnable into fibers and filaments; some are useful in casting; some are moldable; still others can be formulated into coatings. The physical and chemical properties can be changed through choice of monomers, polymerization procedures and other means.
Recently, polyesters have been modified with dicyclopentadiene (DCPD) to result in products having reduced shrinkage upon curing, enhanced hydrophobicity and better economics than the corresponding unmodified polyesters.
More recently, a class of polyesteramides has been developed. Basically, those materials have been the random interpolymerization of a dicarboxylic acid with a diol and a diamine. The products have exhibited a spectrum of properties substantially different from either polyesters or polyamides.
Although DCPD modified polyesters have been useful in making products acceptable in the marketplace, there has been a trade off: those modified polyesters have generally reduced corrosion resistance.